--- foo/foo/foo/boost/utility/result_of.hpp
+++ foo/foo/foo/boost/utility/result_of.hpp
@@ -72,7 +72,7 @@
 // There doesn't seem to be any other way to turn this off such that the presence of
 // the user-defined operator,() below doesn't cause spurious warning all over the place,
 // so unconditionally turn it off.
-#if BOOST_MSVC
+#if defined(BOOST_MSVC) && BOOST_MSVC
 #  pragma warning(disable: 4913) // user defined binary operator ',' exists but no overload could convert all operands, default built-in binary operator ',' used
 #endif